The invention relates to a tire and rim assembly, and more specifically to a run-flat insert that enables a tire and rim assembly to support a vehicle when the tire is deflated.
Various structures have been suggested for use inside a pneumatic tire to support the weight of a vehicle in the event that the tire is deflated. In this specification and the appended claims, such a structure is referred to as a "run-flat insert".
Prior art run-flat inserts have often been made in rigid segments that are fitted around the circumference of a rim, because the structures could not be elastically deformed to fit over the flanges of a rim or inside of a tire; an example of an insert of this type is illustrated in U.S. Pat. No. 4,163,466. Other prior art run-flat inserts have had a separate air chamber, sealed from that of the tire, to enable the insert to carry the load when the tire is deflated; an example of this type of insert is shown in U.S. Pat. No. 2,224,066.
The present invention provides a run-flat insert that is elastically deformable, allows greatly simplified mounting on a rim, is non-pneumatic and therefore is not subject to air-loss failures characteristic of air-chamber run-flat inserts.
There is provided in accordance with one aspect of the invention a run-flat insert for use with a tire and rim assembly. The run-flat insert is made from an elastically deformable polymeric (plastic or elastomeric) material and comprises a structure including an annular band and at least eight, and preferably more circumferentially spaced supporting legs attached to and extending radially inwardly from the radially inner surface of the annular band. In the preferred form, the supporting legs are integral with the annular band, the supporting legs are inclined with respect to the axis of rotation of the run-flat insert; half of the supporting legs are inclined in one direction away from the mid-circumferential plane of the insert and the other half are inclined in the opposite direction away from such plane. Supporting legs on opposite sides of the run-flat insert are inclined outwardly with respect to its mid-circumferential plane. The spacing between adjacent supporting legs on the same side of the mid circumferential plane is at least 30 percent of the circumferential width of a supporting leg at its radially inner end.
There is provided in accordance with another aspect of the invention an assembly of a rim, tire, and run-flat insert. The assembly has a multi-piece rim with two cylindrical coaxial rim members. Each rim member has a radially outer surface with a flange portion formed at the axially outermost end. The assembly also has a tubeless pneumatic tire mounted on the multi-piece rim. The tire has an inner cavity and a pair of bead portions. One of the bead portions is adjacent to each flange portion of the multi-piece rim. With a run-flat insert disposed within the inner cavity of the tire, the insert has an annular band with radially inner and outer surfaces. The radially outer surface has a predetermined maximum diameter, and at least four pairs of circumferentially spaced supporting legs extending radially inwardly from the radially inner surface of the annular band. One-half of the supporting legs are inclined with respect to the axis of rotation of the assembly in one axial direction and one-half of the supporting legs are inclined with respect to the axis of rotation of the assembly in the opposite axial direction. Each supporting leg has a radially outer surface that is adjacent to a bead portion of the tire and a radially inner end that is adjacent to the radially outer surface of one of the rim members. The circumferential spacing between each supporting leg and the adjacent supporting leg inclined in the same direction is at least 30 percent of the circumferential width of a supporting leg at its radially inner end.